As a vehicle occupant restraint device for protecting an occupant from two types of accidents such as a frontal collision and a lateral collision with one product, there has been developed an air belt device in which an airbag accommodated in a shoulder belt of a seat belt is inflated around a shoulder top from a chest in the event of a vehicle collision, thus restraining an occupant.
This air belt device is operated such that an airbag is inflated along a shoulder belt fastened to an occupant in a substantially spindle shape, and the airbag in the belt is directly inflated in the event of the frontal collision, thus increasing a contact area with an occupant's chest, distributing and cushioning impacts applied to the chest. In the event of the lateral collision, an inflated portion of the airbag restrains a region extending from a shoulder top to a temporal region of an occupant, and controls a lateral movement amount of a head, thus preventing a secondary collision due to a side window or an interior structure of a vehicle.
When this air belt device is operated by one retractor, it is necessary to pull out and take up the shoulder belt accommodating the air belt and a lap belt interposing a tongue plate therebetween. Particularly when webbing is pulled out from the retractor, the air belt portion needs to smoothly slide against the webbing such that the air belt portion (a portion of the shoulder belt) having a tongue in which the tongue plate and a gas supply hole are formed in an end thereof is provided at a proper position in a region from the chest to the shoulder while a predetermined amount of lap belt portion is pulled out.
In Patent Literature 1, there is disclosed a seat belt device having a flat tube made of a synthetic resin material and interposed between an airbag body and webbing. In Patent Literature 1, there are disclosed various kinds of tubes that are variously adjusted in rigidity (longitudinal and width directions of the tube) so as to ensure follow-up properties and flexibility when the webbing is pulled out while reducing the sliding resistance of the webbing that has been inserted into and passed through the flat tube. In Patent Literature 1, FIG. 4 illustrates a section of the device when the tube is integrally coupled with the airbag body. The airbag is inflated from the accommodated state of FIG. 4 in the event of a collision, between an occupant restrained by the seat belt and an interior structure of the vehicle. Therefore, a secondary collision between an occupant and the interior structure of the vehicle, such as a steering wheel or a dashboard, is prevented.
An applicant has proposed a vehicle occupant restraint device that overcomes the problems of the seat belt device disclosed in Patent Literature 1, and adopts a slide guide having sufficient rigidity by combining a high rigidity region and a low rigidity region to webbing, thus allowing the webbing to be smoothly pulled out and mounted while a seat belt is fit for an occupant's body type when he or she fastens the seat belt (Patent Literature 2).